Ferrous metal corrosion inhibitor



May '11, 1 965 A. R. WILLEY I FERROUS METAL CORROSION INHIBITOR- Fiied Jan. 3. 1962 INVENTOR. ALLEN B4) W/ZLEY BY M ATI'JRNEYS 3'18 2 ass FERROUS METAL boimosrorz INHIBITOR Allen Ray Willey, Mundelein, lll., assignor to American fan Company, New York, N.Y., a corporation of New erse Filed Jan. 3, 1962, Ser. No. 164,088

6 Claims. (Cl. 220-64) The present invention relates to acomposition for inhibiting corrosion of a ferrous metal and in particular to the inhibition of corrosion of sheet metal havinga ferrous base such as tinplate by adding to the-corrosion inducing medium a composition consisting essentially of a known, standard corrosion inhibitor and a particular vinyl resin as a synergist therefor.

The present invention will be described hereinafter with particular reference to inhibiting corrosion on the inside of a sheet metal can by a product packed therein. However, ,itis to be understood that the corrosion inhibitorcomposition havingfutility in the instant invention may also be used to inhibit corrosion of ferrous metals having. different shapes and exposed to different corroding environments. By, ferrous metals, as used herein, is meant uncoated steel and steel having a thin coating of non-ferrous metal such as tin or aluminum thereon. I I v Many of the liquid comestibles packed in sheet metal cans, particularly liquid fruit juices and other aqueous drinks containing fruit flavors, have a corroding effect on the metal of the can. This problem is recognized by the prior art and patents have been issued teaching means of alleviating this corrosion problem. Two such patents are US. Patents 2,168,107 and 2,914,213. However, one of the problems experienced with these prior art inhibitors and inhibitor compositions is that when present in an amount sufiicient to provide an efficient inhibiting action, off-odors. and off-flavors in the packed product result. The undesirability of such off-odors .and off-flavors in canned comestibles is obvious.

It is, therefore, an object of the present invention to provide a composition which is highly efficient in inhibiting corrosion of ferrous metals when present in the corroding medium in extremely small amounts.

Another object isv to provide a composition for inhibiting corrosion 'of the interior surface of a packed ferrous 4 sheet metal can which, when present in the packed product iii-amounts sufficient to provide efficient corrosion inhibition, imparts no off-odors or off-flavors to the product.

' Yet another object is to provide a ferrous sheet metal can having an odor free and taste free corrosion inhibiting compositioncontained therein.

A further object is to provide a canned product having 3,182,853 Patented May 11,1965

of the instant invention can be any of those known and disclosed in the prior art as suitable for inhibiting the corrosion of the interior of a sheet metal can. Specific examples of such corrosion inhibitors are amino or hydrox- -ylcontaining compounds having an aliphatic sulfhydryl group, tin ion either in the stannous or stannic state, and

carbon monoxide. Specific sulfhydryls or those capable of hydrolyzing to sulfhydryls within the above definition are cystamine, cysteine, tetramethylthiuram monosulfide,

mercaptobenzothiazol, and such compounds having an amino group substituted thereon, ring-opened isopropyl thiamine disulfide, acetyl mercapto succinic anhydride,

ammonium thiocyanate, and thiourea.

For the purpose of the invention, the above mentioned known corrosion-inhibitors are present in the over-all inhibiting composition in an amount of from 1 to and preferably about 15% by weight. Further, best corrosion inhibition is obtained by the useiof cystamine, cysteine or ammonium thiocyanate, making these compounds preferred.

Each of the above listed materials, when used alone has a corrosion inhibiting effect on the ferrous metal of a sheet metal can. thereof necessary toprovide good corrosion inhibition must be relatively large. With these large amounts, especially with'the sulfhyd-ryls, severe problems of taste and odor occur.

It has now been discovered that when a known inhibitor is combined with the aforementioned polyvinyl resins, not only is it possible to provide efiicient corrosionprotection for the'ferrous metal of the can with much lower concentrations of the inhibitor, but also the taste andodor problems P TQ uced by the sulfhydryls are 4 used alone without being'combined with a known cora corrosion inhibit-ing'composition therein (for the ferrous metal of the can which imparts no offensive odor or flavor to the canned product.

Numerous'other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the-accompanying drawing, discloses apreferred embodimen-t thereof.

rosion inhibitor, are often corrosion accelerators. However, it has been found that by combining these substituted, polyvinyl resins with the known corrosion inhibitors, any corrosion accelerating tendency is not only eliminated, but the corrosion inhibiting action of the known inhibitors is markedly enhanced;

The specific substituted polyvinyl resins found suitable inthe instant invention are poly-N-vinyl-2-pyrrolidone (hereinafter referred to as PVP),poly-N-vinyl-S-methyl- 2-oxazolidinone (hereinaften referred to as PVC), and copolymers of N-vinyl-5-methyl-2-oxazolidinone and vinyl acetate (hereinafter referred to as PVO-VA).

The average molecular weight of .each of the vinyl polymers isbetween 100,000 and 200,000. The PVP and PVO are water soluble. -The PVO-VA is slightly soluble in water and is soluble in organic solvents. lFurther, each polymer has film forming properties.

In the instant invention, acting as a synergist for the known corrosion inhibitors, the substituted vinyl polymers are used in an amount of 10 to 1,000, and preferably about 30 parts per million parts of corroding medium. When the inhibitor composition is used on the interior of a ferrous metal can, the corroding medium is the product packed in the can.

To perform its inhibiting function, the composition of the instant invention may be applied to the ferrous metal surface, which is to be protected, as a solution from which the liquid carrier (preferably water) is evaporated to leave a film of the inhibitor composition. contacted bya corroding medium such as moisture, this film will break down, releasing the "composition to perform its corrosion inhibiting function.

.In otherinstances where theferrousmetal to be protected has a resinous coating applied over its surface, the inhibiting composition can be dispersed uniformly throughout the solution from which the resin coating is However, when so used, the amounts Upon being to be applied. The'solid film on the metal surface existing after application of the resin solution and drying thereof, will contain the-inhibitor compositon. In this case the resin coating provides the main barrier against corrosion; 'but the inhibitor composition contained therec omestibles, the inhibitor composition" may be added directly to the product being packed in the sheet metal can. In this case the product itself, or a portion of it, while being the corroding medium, is also the vehicle or carrier for the inhibiting composition.

As, a preferred or exemplary embodiment of the instant invention, the drawing shows a tin-plate can having a body 10, and upper and lower ends thereon 11, 12 respectively, made integral with'the body by any suitable means'such as upper and lower double seams 13, 14 respectively.

Adhering to the interior surface of the can body 10 is a film 15, composed of cysteine as the known inhibitor and PVP as the substituted vinyl resin synergist therefor. The film 15 is initially applied as an aqueous solution containing the cysteine and PVP in a weight ratio of about 1 to 7. Sutficient of the aqueous solution is applied to provide about 35 parts of dry, inhibitor composition on the inside surface of the can per million parts of the carbonated beverage product 16 within the can.

Because of its film forming property, the PVP retains the dry,-inhibiting composition on the inside surface of the can body. Upon being contacted with the aqueous product 16, the water solubility of the PVP causes the film to dissolve gradually, thereby releasing the inhibiting composition into the product. As it dissolves into the product, the inhibitor composition performs its function of inhibiting corrosion of the interior of the tinplate can by the product 16. I

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes 4 may be made in the matter of the ingredients, the identity and the proportions of the formulation, and that changes may be made in the form, construction and arrangement of the parts of the article without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. A composition for inhibiting corrosion of a ferrous metal comprising the combination ,of a corrosion inhibitor for ferrous metal and a polymer selected from the group consisting of poly-N-vinyl-2-pyrrolidone, poly-N- vinyl-S-methyl-Z-oxaZoIidinone, a copolymer of N-vinyl-5- methyl-Z-oxazolidinone and vinyl acetate, and mixtures thereof.

2. The composition set forth in claim polymer is poly-N-vinyl-2-pyrrolidone.

3. The composition set forth in claim 1 wherein said polymer is poly-N-vinyl S-methyl-2-oxazolidinone.

1 wherein said 4. The composition set forth in claim 1 wherein said polymer is a copolymer of N-vinyl-5-methyl-2-oxazolidinone and vinyl acetate.

5. The composition set forth in claim 1 wherein said inhibitor and said polymer are combined in a weight ratio of from 1/99 to /50.

6. A container at least. aportion of which is ferrous metal, said container having adhered to only a portion of its interior surface the composition of claim 1 as a corrosion inhibitor for said metal.

References Cited by' the Examiner UNITED STATES PATENTS 1,613,808 1/27 Schreiber 206-84 2,466,530 4/49 Blair et a1. 106-14 X 2,632,750 3/53 Justice 260-883 2,682,336 6/54 Moberly 206-84 2,764,313 9/56 Foley et a1. 220-64*- 2,821,519 1/58 Glickman 260-883 2,912,136 11/59 Redmond et al 220-63 THERON E. CONDON, Primary Examiner.

FRANKLIN T. GARRETT, GEORGE 0. RALSTON,

EARLE J. DRUMMOND, Examiners. 

1. A COMPOSITION FOR INHIBITING CORROSION OF A FERROUS METAL COMPRISING THE COMBINATION OF A CORROSION INHIBITOR FOR FERROUS METAL AND A POLYMER SELECTED FROM THE GROUP CONSISTING OF POLY-N-VINYL-2-PYRROLIDONE, POLY-NVINYL-5-METHYL-2-OXAZOLIDINONE, A COPOLYMER OF N-VINYL-5METHYL-2-OXAZOLIDINONE AND VINYL ACETATE, AND MIXTURES THEREOF. 